CVE-2026-73270: httpd mod_auth directory protection bypassed by request path casing on case-insensitive filesystems

Severity: high (CVSS 8.2 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-01 · updated 2026-09-08
Weakness: CWE-178

Description

Improper Handling of Case Sensitivity vulnerability in Erlang/OTP inets httpd allows a remote unauthenticated attacker to read files inside a mod_auth protected directory by requesting them with different casing, on deployments whose filesystem is case-insensitive. mod_auth:secret_path/3 decides whether a resolved filesystem path lies inside a protected directory block by running the configured directory path through re:run/3 without the caseless option. A request for /secret/file against a directory configured as /Secret therefore does not match, so the request is treated as unprotected and no authentication challenge is issued, while the filesystem resolves the differently cased path to the same file and mod_get serves it. Deployments on case-sensitive filesystems are unaffected, because there the filesystem itself rejects the mismatched casing. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Affected products

Erlang OTP: from 17.0 before 27.3.4.17; from 28.0 before 28.5.0.6; from 29.0 before 29.0.6; from 5.10 before 9.3.2.7; from 9.4 before 9.6.2.3; from 9.7 before 9.7.2 — fixed in 27.3.4.17, 28.5.0.6, 29.0.6, 9.3.2.7, 9.6.2.3, 9.7.2

How to fix

Upgrade to a fixed version: Erlang OTP 27.3.4.17, 28.5.0.6, 29.0.6, 9.3.2.7. Check the vendor advisory for mitigations.

References

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